Molecular basis for modulation of biological function by alternate splicing of the Wilms' tumor suppressor protein

Alternate splicing, leading to the insertion of the tripeptide KTS in the l inker between the third and fourth C2H2 zinc fingers, changes both the DNA- binding function and the subnuclear localization of the Wilms' tumor suppre ssor protein (WT1). We have used NMR relaxation experiments to determine th e molecular basis for the differing DNA recognition properties of the WT1-K TS and WT1+KTS isoforms. Our results show that the KTS insertion increases the flexibility of the linker between fingers 3 and 4 and abrogates binding of the fourth zinc finger to its cognate site in the DNA major groove. Thi s represents a mechanism whereby a single zinc-finger gene can be used, thr ough alternate splicing, to fulfill different functions in the cell.